For years there has been interest in recovering thermoplastic insulation materials for reuse by plastic molders and extruders. However, the scrap plastic insulation materials are typically not up to the quality of virgin thermoplastic materials. As such, such material has not gained much acceptance for use in lieu of virgin thermoplastic materials because of the difference in quality and also the difference in price.
In the present spirit of wishing to recycle all useful products in lieu of consuming non-renewable mineral ores, there has been an upsurge in the reclamation of such mineral ores such as copper and aluminum from insulated wire. A by-product of such a reclamation procedure is the wire insulation itself. As noted earlier, such recycled insulation materials are not high demand. Thus, the recycling of copper and aluminum wire, for example, is currently plagued with the problem that arises from the need to dispose of the shredder residue and dust i.e., the wire plastic coatings and other natural casings and housing as well as residual wire cuttings and fines which are produced as a waste product off of the wire recycling equipment. The wire reclamation solid waste is currently either managed as a solid or a hazardous waste depending on the lead (Pb) leachability as revealed by the Extraction Procedure Toxicity (EPT) or Toxicity Characteristics Leaching Procedure (TCLP) extraction test defined by the Resource Conservation and Recovery Act (RCRA). The TCLP extraction test predicts the effect of decomposing organic material in a landfill on wastes being considered for landfill waste disposal. When organic material decomposes, acetic acid is formed. Thus, in the TCLP extraction test, both water and acetic acid are used to extract leachable heavy metals, such as lead, from the waste, which are then quantified. Most such solid waste currently fails the TCLP regulatory limit of 5.0 ppm for lead and thus is currently considered a hazardous waste in the United States. Likewise scrap, including plastics and filter dust, from automobile shredder operations to reclaim metals in the Netherlands has been declared hazardous by the government due to possible heavy metal contamination.
Thus, there is a need for a method to safely dispose of shredder residues and filter dust, including reclaimed wire insulation and fluff and automobile shredder residues, or to render it safe for disposal without concern of leaching of heavy metals such as lead.
The environmental hazard of shredder residues and filter dust from which leachable amounts of lead greater than the toxic levels specified by the Environmental Protection Agency (EPA) could be somewhat diminished by mixing such residues and dust with other types of residues not containing lead, such that the resulting mixture is within the toxic levels for lead. However, such a practice is not allowed by the EPA, i.e., hazardous wastes cannot be mixed with non-hazardous wastes to dilute the levels of lead below toxic levels. Thus, it is highly desirable to reduce the amount of lead leached from such waste material and other solid waste containing leachable lead to an amount below the toxic level specified by the EPA. The invention herein is a solution to this problem. More specifically, it is a method of treating solid waste materials, such as shredder residues and filter dust and mixtures containing such solid waste materials, so as to reduce the amounts of lead leached therefrom to a level below the toxic level specified by the EPA. Stated differently, the invention herein is a method of immobilizing, or insolubilizing, lead in solid waste produced by metal reclamation processes. The method is convenient, quite simple, very efficient, applicable over a wide pH range, and relatively low cost. An important advantage of the method of the present invention is that the method can be performed in a totally "enclosed" environment, thereby exempting the practice of the present invention in this manner from RCRA Part B permitting. The method is, therefore, commercially extraordinarily attractive as well being environmentally beneficial.